In a typical liquid crystal display, a backlight module is used to provide a planar light source for illuminating the liquid crystal display. In general, the backlight module includes a light source and a light guide plate, the light source disposed at a side of the light guide plate. The light guide plate transforms diverging light rays emitted from the light source into planar light rays, and directs the planar light rays to a liquid crystal panel of the liquid crystal display.
Referring to FIG. 6, a typical backlight module 10 is shown. The backlight module 10 includes a light guide plate 11, a lamp tube 12, a reflector 13, a reflective plate 14, and a plurality of optical sheets such as a light diffusion plate 15, first and second prism sheet 16 and 17. The light guide plate 11 includes a light reflective surface 112 and a light emitting surface 113 on opposite sides of the light guide plate 1, and further includes a light incident surface 111 adjoining the light reflective surface 112 and the light emitting surface 113. The lamp tube 12 is disposed adjacent to the light incident surface 111 of the light guide plate 11. The reflector 13 partly surrounds the lamp tube 12 and reflects light rays projecting out of the lamp tube 12 to the light guide plate 11. The reflective plate 14 is positioned underneath the light reflective surface 112 for reflecting light rays projecting out of the reflective surface 112 back into the light guide plate 11. The light diffusion plate 15 and the first and second prism sheets 16 and 17 are stacked on the light emitting surface 113 for diffusing emitted light rays and collimating the emitted light rays uniformly to improve a brightness uniformity.
When the backlight module 10 is in use, light rays from the lamp tube 12 pass through the light incident surface 111 and enter the light guide plate 11. The light rays are reflected and refracted by the light guide plate 11 before surface light rays are outputted from the light emitting surface 113. However, the elements of the backlight module 10, such as the light guide plate 11, the lamp tube 12, and the reflector 13 are normally not compactly attached together, thus, gaps exist therebetween. An amount of light rays emitted from the lamp tube 12 escapes through these gaps, and are not emitted to the light guide plate 11, thereby utilization of the light rays is reduced.
Referring to FIG. 7, in order to overcome the above mentioned shortcoming, another typical backlight module 20 is provided. The backlight module 20 is similar to the backlight module 10, except that a light guide plate 21 is different from the light guide plate 11. The light guide plate 21 defines a receiving tunnel 211 in an end thereof. A lamp tube 22 is inserted into the receiving tunnel 211. Accordingly, light rays from the lamp tube 22 could be substantially reflected and refracted into the light guide plate 21, with a significantly small amount of light rays escaping through the gaps between the light guide plate 21 and a reflector 23.
However, the backlight module 20 is not conveniently assembled. Referring to FIG. 8, typically, two electrodes (not shown) of the lamp tube 22 are electrically connected to two lamp wires 222 correspondingly. The two electrodes of the lamp tube 22 are correspondingly inserted into two electrode holders 221 that have a lamp wire 222 that passes through each electrode holder 221. An end of each lamp wire 222 is connected to a connector 223. The lamp tube 22 can be electrically connected to an external electric power (not shown) via the two lamp wires 222 and the connector 223. Since a size of the electrode holder 221 is larger than a diameter of the receiving tunnel 211, the lamp tube 22 assembled with the two electrode holders 221 cannot be inserted into the receiving tunnel 211 directly. Accordingly, when the backlight module 20 is assembled, the lamp tube 22 should be inserted into the receiving tunnel 211 of the light guide plate 21 first before the lamp wires 222 are electrically welded to the electrodes of the lamp tube 22. Afterwards, the electrode holders 221 are assembled to fix the electrodes of the lamp tube 22 on an exterior of the light guide plate 21. The lamp wires 222 are introduced out from the corresponding electrode holder 221. Therefore, assembling the backlight module 20 is complicated and difficult. In addition, pattern dots 213 formed on a light reflective surface 212 of the light guide plate 21 are prone to being damaged when assembling the lamp wires 222 and electrode holders 221, thus the backlight module 20 has a relatively poor optical performance. Furthermore, the light guide plate 21 is typically manufactured by using an injection molding method/technology, thereby forming the receiving tunnel 211 in the light guide plate 21 is complex and costly.
What is needed, therefore, is a backlight module that overcome the above mentioned shortcomings.